Biogenic emissions and CO2 gas exchange investigated on four Mediterranean shrubs

In order to investigate the impact of plant physiology on emissions of biogenic volatile organic compounds monoterpene emission rates from Rosmarinus officinalis (L.) and Pistacia lentiscus (L.) and isoprene emission rates from Erica arborea (L.) and Myrtus communis (L.) were determined. The study, an activity in the framework of BEMA (Biogenic Emissions in the Mediterranean Area), was carried out in May 1994 at Castelporziano near Rome in Italy, using a dynamic enclosure technique combined with recording CO2 gas exchange, temperature and irradiance data. The monoterpenes dominating the emission pattern were 1,8-cineol, alpha-pinene and beta-pinene for rosemary and alpha-pinene, linalool and beta-pinene + sabinene for pistachio. Total monoterpene emission rates standardized to 30 degrees C of 1.84 +/- 0.24 and 0.35 +/- 0.04 mu g C g(-1) dw h(-1) were found for rosemary and pistachio, respectively (on a leaf dry weight basis). Myrtle emitted 22.2 +/- 4.9 mu g C g(-1) dw h(-1) at standard conditions (30 degrees C, PAR 1000 mu mol photons m(-2) s(-1)) as isoprene and erica 5.61 mu g C g(-1) dw h(-1). The carbon loss due to terpenoid emissions per photosynthetically carbon uptake was about 0.01-0.1% for the monoterpene emitters. The isoprene emitting shrubs lost 0-0.9% of the assimilated carbon. The rapid induction of emissions in the sun after temporary shading indicates that isoprene emissions were closely linked to photosynthesis. A higher proportion of the assimilated carbon was lost as isoprene under conditions of high light and temperature compared to the morning and evening hours. (C) 1997 Elsevier Science Ltd.